A series of revelations this week shows the federal probe of President Donald Trump’s alleged campaign ties to Russia has centered around social media propaganda.

Special counsel Robert Mueller’s team of prosecutors and FBI agents have focused on Russian efforts to spread fake news stories on Facebook and Twitter, which were frequently amplified by Trump on the campaign trail, reported Bloomberg Politics.

Facebook acknowledged last week that Russian companies had bought $100,000 in ads intended to help the Trump campaign and confirmed the shutdown of multiple pages used by Russian agents to promote anti-immigration rallies echoing Islamophobic conspiracy theories spread among right-wing websites like Breitbart News.

That relatively small ad buy would be nearly useless — unless they were targeted to specific audiences, or even drilled down to specific users.

Both Mueller’s team and congressional investigators are examining whether the Trump campaign’s digital operation — which was overseen by son-in-law Jared Kushner — helped guide Russia’s sophisticated targeting of social media users.

The data firm Cambridge Analytica, headed by Trump megadonor Robert Mercer, used personal information harvested from Facebook users to build psychological profiles based on 5,000 separate pieces of data on 220 million American voters, which the company used to target their emotions and influence their thoughts and behavior.

That allowed the Trump campaign to turn Facebook into a propaganda cannon, and investigators are looking into whether Kushner helped Russia bombard American voters with fake news intended to help Trump win.

The FBI is reportedly investigating Russian state-owned media outlets Sputnik and RT for disinformation campaigns aimed at American consumers, who in turn unwittingly spread Kremlin propaganda on their own news feeds.

Reports about Mueller’s “red-hot” focus on social media comes as bipartisan leaders on the Senate Intelligence Committee have called on Facebook and other social media companies to be more transparent about foreign influence campaigns and other election activities.

The social media giant has not described the ads and believes the information may be protected under the Electronic Communications Privacy Act, and it refuses to say how it discovered 470 fake accounts and pages linked to the ads.

Journalist Casey Michel, who tracks U.S. secession movements, discovered a Facebook group linked to Russia that organized anti-immigrant and anti-Hillary Clinton rallies in Texas in the days ahead of the presidential election, reported Business Insider.

The “Heart of Texas” group promoted anti-Clinton and anti-establishment themes, along with secessionist ideas, in awkwardly phrased and misspelled memes that betrayed their non-U.S. origins — but the page boasted 225,000 followers last summer.

It’s not clear how many people actually showed up at those rallies, but it shows how the Kremlin hoped to use propaganda to influence American politics ahead of the election and promote fringe views.

“This is the next step,” Clint Watts, a former FBI agent and cybersecurity expert, told The Daily Beast. “The objective of influence is to create behavior change. The simplest behavior is to have someone disseminate propaganda that Russia created and seeded. The second part of behavior influence is when you can get people to physically do something.”

Watts told congressional investigators in March that Russian agents exploited the inability of many social media users to properly weigh evidence — and he said those efforts were specifically targeted to the most famous and powerful Twitter user in the world.

“Part of the reason active measures have worked in this election is because the commander-in-chief has used active measures at times against his opponents,” Watts testified.